Progress Reports

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Power Sector Programs – Progress Report

Under the Clean Air Act, EPA implements several regulations that affect power plants, including the Acid Rain Program (ARP), the Cross-State Air Pollution Rule (CSAPR), the CSAPR Update, and the Mercury and Air Toxics Standards (MATS). These programs require fossil fuel-fired electric generating units to reduce emissions of sulfur dioxide (SO₂), nitrogen oxides (NOₓ), and hazardous air pollutants including mercury (Hg) to protect human health and the environment. This reporting year marks the sixth year of CSAPR implementation, the fourth year of the CSAPR Update implementation, the twenty-sixth year of the ARP, and the fourth year of MATS implementation in which the majority of sources were required to report emissions for the full year. This report summarizes annual progress through 2020, highlighting data that EPA systematically collects on emissions for all four programs, on compliance, and environmental effects for the ARP and CSAPR. Transparency and data availability are a hallmark of these programs, and a cornerstone of their success.

SO₂, NOₓ, and hazardous air pollutants (HAPs), including mercury, are fossil fuel combustion byproducts that affect public health and the environment. SO₂ and NOₓ, and their sulfate and nitrate byproducts, are transported downwind and deposited as acid rain at levels harmful to sensitive ecosystems in many areas of the country. These pollutants also contribute to the formation of fine particles (sulfates and nitrates) and ground-level ozone that are associated with significant human health effects and regional haze. Atmospheric mercury deposition accumulates in fish to levels of concern for human health and the health of fish-eating wildlife.

The ARP, CSAPR, CSAPR Update and MATS have delivered substantial reductions in power sector emissions of SO₂, NOₓ, and hazardous air pollutants, along with significant improvements in air quality and the environment. In addition to the requirement of the power sector emission control programs described in this report, a variety of power industry trends have contributed to further declines of SO₂, NOₓ, and hazardous air pollutant emissions.

EPA data in this report are current as of May 2021 and may differ from past or future reports as a result of resubmissions by sources and ongoing data quality assurance activities.

Read historical reports of EPA's Clean Air Markets Programs
CSAPR Program Map

2020 ARP, CSAPR, and MATS at a Glance

  • Annual SO₂ emissions:
    CSAPR - 497 thousand tons (94 percent below 2005)
    ARP - 778 thousand tons (95 percent below 1990)
  • Annual NOₓ emissions:
    CSAPR - 405 thousand tons (81 percent below 2005)
    ARP - 721 thousand tons (86 percent below 2000)
  • CSAPR ozone season NOₓ emissions: 232 thousand tons (49 percent below 2015)
  • Compliance: 100 percent compliance for power plants in the market-based ARP and CSAPR allowance trading programs.
  • Emissions reported under MATS:
    Mercury - 2.6 tons (91 percent below 2010)
  • Ambient particulate sulfate concentrations: The eastern United States has shown substantial improvement, decreasing 47 to 83 percent between 2000-2002 and 2017–2019.
  • Ozone NAAQS attainment: Based on 2017-2019 data, 90 of the 92 areas in the East originally designated as nonattainment for the 1997 ozone NAAQS are now meeting the standard, while the remaining 2 areas had incomplete data.
  • PM₂.₅ NAAQS attainment: Based on 2017-2019 data, 36 of the 39 areas in the East originally designated as nonattainment for the 1997 PM₂.₅ NAAQS are now meeting the standard (one area has incomplete data).
  • Wet sulfate deposition: All areas of the eastern United States have shown significant improvement with an overall 68 percent reduction in wet sulfate deposition from 2000-2002 to 2017–2019.
  • Levels of acid neutralizing capacity (ANC): This indicator of recovery improved (i.e., increased) significantly from 1990 levels at lake and stream monitoring sites in the Adirondack region, New England and the Catskill mountains.